Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue (including amounts from related parties of $2,813, $22,536 and $18,966 during the years ended December 31, 2020, 2019 and 2018, respectively)	$ 42,722	$ 42,736	$ 38,419
Operating expenses
Research and development	76,961	65,612	54,262
General and administrative	36,818	32,592	21,380
Total operating expenses	113,779	98,204	75,642
Loss from operations	(71,057)	(55,468)	(37,223)
Interest income	1,508	4,074	1,616
Unrealized gain on equity securities	41,498
Interest and other expense, net	(4,077)	(4,350)	290
Net loss	$ (32,128)	$ (55,744)	$ (35,317)
Net loss per share, basic and diluted	$ (0.99)	$ (2.43)	$ (6.13)
Weighted-average shares used in computing basic and diluted net loss per share	32,573,469	22,958,577	5,758,875